When rotary drilling deep wells into the Earth (such as the drilling of oil wells, gas wells and similar boreholes), a wide variety of geographic formations will be encountered at various depth levels. During a typical drill procedure, a substantial amount of drilling mud must first be premixed in a large tank or vessel known as a mud pit. Generally, heavy bags of dry mud (about 50 pounds each) are injected into a mixing tank through a hopper, and the dry mud is mixed with water and other desired compounds in the hopper and transported into the tank. Mud is a substance which is premixed from a bag with one or more liquids (usually water, and sometimes other caustic materials) prior to injection into the hole. The other desired compounds are preselected based on the drilling requirements, and may include, for example, chemicals, liquid and/or gas. The mud is premixed typically so that it is heavier than water in order to pick up the cuttings. A exemplary weight of the mud is between 11 and 12 pounds of mud per gallon, and usually is dependent on the job site characteristics and requirements.
A representative mud pit may be a 10 feet by 30 feet and about 12 feet high, which holds about 400 barrels (bbl) of mud. The mud pit is usually connected to the drilling rig by way of a mud line and mud pump which injects the mud into the top of the drill pipe. In some typical drilling procedures, over 1200 bags of mud may be used on site. To create mud for a 3000 foot well, for example, and at $50 per bag of mud, it may cost between $75,000 and $100,000 to create the mud on site. Thus, the requirement of transporting and using mud at a drilling site can be a significant expense.
As partially illustrated in FIG. 1, drilling rigs usually employ a derrick that extends above the well drilling platform and is constructed so that it can support joints of drill pipe connected end-to-end during the drilling operation. As the drill bit is forced into the Earth's subsurface, additional pipe joints are added to the connection (or, “string”) of drill pipes. The drill string pipes each have an internal longitudinal bore for carrying drilling mud from the well drilling platform to a drill bit supported at the lower or distal end of the drill string. The derrick may be set up adjacent to the borehole to begin the drilling process. A typical drilling rig may use a 14 inch drilling bit to begin the drilling process. A typical drilling bit contains holes (e.g., openings or apertures) on its drilling portion, which are in fluid or mud flow communication with the mud through tubing connected to the mud pit. In this regard, as the drilling procedure commences and continues to drill down into the hole, premixed clean mud can be injected to the borehole concurrently, and hence, into the hole, through the drill bit. Because the entire hole is securely pressurized (as is common in conventional down hole drilling procedures), the drilling mud that is injected into the hole is subsequently forced to return to the Earth surface. However, during the drilling process, the Earthen soil, which is excavated through the drilling process, also contains one or more particles or heavier particulates which get caught in the drilling mud and begin to follow the drilling mud flow pattern. As a consequence, as the drilling mud returns to the surface, so does the particles and particulates. These particles or particulates are referred to in the industry as “cuttings” (e.g., the particles that are cut away from the Earth to create the hole). Representative cuttings may include granite, rock, coal, sand, shale, water, gas and like geographic minerals found in the Earthen crust (including, for example, potentially environmentally hazardous materials such as oil). In some instances, the cuttings attach or adhere themselves to the drilling mud.
The use of mud also means that several characteristics of the drilling process must be maintained, so that (for example) the mud's viscosity, density, and other properties must be maintained to predetermined limits, otherwise there is a significant risk that the drilling process may be adversely affected. Nevertheless, drilling mud is useful, as it lubricates the drill bit during the drilling process while allowing for the each transportation of cuttings. The drilling mud is typically mixed to be a heavy viscous liquid, and other compounds (such as, for example, diesel, crude oil, and other non-water soluble petroleum based products) may be added to the mud to facilitate the mud's lubricating characteristics.
Depending on the project, a typical drilling may go anywhere from 25 feet below the Earth's surface to well over 20,000 feet below the Earth's surface. Every drilling project is unique, and may require different parameters for use. Thus, for example, a short range depth hole may only require a small diameter hole to be dug, whereas a long range depth hole may require a much larger diameter hole to be dug. Thus, for example, a 7000 foot deep hole may typically require the creation of an approximately 18 inch diameter surface casing substantially throughout the length of the hole being dug. As the hole is being slowly dug, the drilling bit is removed from the hole, and surface casing is inserted into the diameter of the hole in order to create a reinforcement wall or barrier which also prevents any external material (such as gas or oil) from coming to the surface during the pressurized drilling process. Surface casing pipe is typically formed of a metal or metal compound and usually comes in 20 to 30 foot lengths which can be interconnectable to allow longer length casings (as may be needed for longer depth holes). The diameter of the hole being dug is generally larger than the surface casing inserted into the hole. Once the casing is installed, cement is then inserted into the outer portion of the casing surface, thereby creating a permanent down hole bore. To help the cement cure, calcium chloride may be added to the cement. Calcium chloride in the cement also helps the cement to dry in adjacent water pockets underneath the Earth's surface. By cementing the casing to the Earth, a barrier is created which prevents any liquid, gas or other undesirably contaminants nearby from escaping to the Earth's surface during the drilling process.
The process of drilling a long-range down hole well is repetitive and done in sections. Thus, for example, the first 1000 feet is drilled and then sealed through the casing/cement structure. Then, the next 1000 feet is drilled and sealed through the casing/cement structure. This repetition continues until the desired depth of the hole is reached. During this entire process, drilling mud is continuously injected into the hole through the drill bit. Because the system is pressurized, the used drilling mud as well as any cuttings are forced to return to the Earth surface (hereafter collectively referred to as “dirty mud”).
When the dirty mud returns to the surface, the dirty mud may thereafter be transported to a conventional prior art shaker or shaker system containing a plurality of screens. The shaker system is utilized to try to separate some of the mud from the cuttings. Namely, the shaker attempts to separate the used mud from the larger cuttings so that some of the mud may fall through the screens and into the clean mud tank. The larger cuttings and clumped or adhered mud may then continue on to be transported to a large container for disposal to a land farm or alternatively, be transported to an empty Earth pit (or, reserve pit, as they are sometimes called) which has already been dug on site. The empty Earth pit may have, for example, the dimensions of 50 feet by 120 feet by 12 feet deep, and the Earthen dirt which was dug up to create the empty Earth pit is usually displaced off to the side of the empty Earth pit in a mound. These type of Earth pits may contain a variety of elements, including drilling mud, cuttings and other solid wastes. Unfortunately, there are numerous documented events where these pits have failed to contain the waste, which results in the contamination of the local environment and/or water aquifers. As a result, and due to the change in many recent laws, the used mud which will be placed in the empty Earth pit must subsequently be removed and transported to a recycling land farm, and the Earthen dirt which was dug up to create the empty Earth pit must thereafter be replaced back into the empty pit. A land farm is an offsite area which is used to mix the dirty mud with one or more chemicals or manure (such as chicken manure or sheep manure, for example), which heats up the dirty mud through a chemical decomposition process in an attempt to evaporatively cleanse the chemicals from the dirty mud. Such land farms are usually far away from the drilling site, and require heavy equipment used to till and rotor the dirty mud with the manure in order for the chemical decomposition process to continue. At some point in the future (generally, on the order of years), the dirty mud can then be cleared for reintegration back into the Earth's soil. This process leads to environmental pollution. Moreover, the cost for transporting the dirty mud to an offsite land farm is very expensive (a 3000 foot well in La Plata County, Colorado recently cost almost $300,000 to transport the dirty mud to an offsite land farm). Additionally, third party companies must be hired to further clean the dirty mud, and also certify that the area where the drilling occurred is environmentally safe after the drilling process.
Another type of land farm occurs where the dirty mud is transported to an offsite area and injected deep into the Earth through a borehole well for permanent storage. The well stays open until it is full of dirty mud, and then the well is permanently closed. Again, this type of dirty mud storage may also cause environmental pollution in the Earth soil.
Conventional drilling processes have many disadvantages. For example, there is a significant cost for environmental remediation which is legally required by state and federal agencies. Additionally, there is still a significant possibility of environmental pollution if the drilling process is done incorrectly or with disregard to the local environment. Moreover, allowing the cuttings to remain in the mud during the drilling process is problematic because the particulates will likely have an adverse impact on the drilling mud (and hence, the drilling operation). Finally, the cost for remediation can range from $50,000 to $250,000 or more (protecting the area from local wildlife through fences, nets, tarps and like instruments, etc).
It is therefore an exemplary feature of the present invention to provide a novel method, system or apparatus for processing drilling mud in a closed loop such that any undesirable particulate such as drill cuttings may be substantially, if not completely, separated from the drilling mud while at the same time allowing the recycled drilling mud to be continuously circulated with any drilling mud.